The present invention relates to an apparatus and a method for polishing continuously and cooling uniformly the barrel or face of a rolling mill work roll mounted in its stand. The invention is applicable to the rolling of flat metallurgical products and more particularly to the hot rolling of steel strips.
Since users are becoming more and more demanding as regards the quality of the surface appearance of rolled strips, it is important nowadays to improve certain rolling factors which have an influence on this quality.
Among these factors three should be mentioned the physical state of the roll face, which should have a correct profile and a suitable and uniform standard of roughness, and the thermal state of this face which should have as uniform surface temperatures as possible over its entire zone in contact with the metallurgical product.
Concerning the physical state of the face, is should be mentioned that, during hot rolling of strips, oxide incrustations often adhere to the rolls especially those of the first three finishing stands. Contacting the strips during processing, these incrustations produce imprints in the faces of these strips and substantially impair their outward appearance. This results in a considerable amount of rejection and downgrading in rolled strips. Moreover these same incrustations cause rapid damaging of the roll faces, and result in the rolls having to be replaced frequently.
To maintain the profile of the roll face and to remove oxide incrustations, a device has already been provided for polishing this face during the rotational movement of the roll during rolling. This known device comprises mainly a pumice stone fixed to a support having a screwthreaded bore through which a worm extends which is disposed parallel to the axis of rotation of the roll, over the entire length of the roll face. By the action of a reversible electric motor the worm rotates slowly about its longitudinal axis in one direction over a travel corresponding to the length of the face and in the opposite direction over the reverse travel. Therefore, the pumice stone sweeps the face of the roll with an alternating movement over the entire length of the said face, and polishes the latter to a greater or less degree during rolling.
However, the pumice stone is particularly short, and bears against the roll face only over a relatively short length. Also, the pumice stone is displaced slowly along the face, and returns to any one zone after several revolutions of the roll. Consequently the known device can smooth the roll face only locally and temporarily, and removes oxide incrustations only periodically and locally.
Concerning the thermal state of the roll face, it must be pointed out that during rolling the rolls are already cooled by a series of jets of water sprayed on to a roll face zone situated slightly downstream of the zone of contact with the steel strip, considered in the direction of rotation of these rolls.
However, the water projected on to the rolls is not collected, and is dispersed uselessly below these rolls. The cooling of the roll faces with water thus results from rapid contact between this water and the roll face, and can take place only to an irregular extent over the entire length of the said face.